Litz said he intends to be involved in efforts to support the Regional Greenhouse Gas Initiative, a climate change program he helped craft while at DEC, against challenges being waged by conservative opponents.

He said the center expects to join the state in rebuffing a lawsuit against RGGI, which limits greenhouse gas emissions from power plants, launched last month by the group Americans for Prosperity, which is linked to conservative petrochemical billionaires Charles and David Koch.

Most recently, Litz was a senior fellow at the World Resources Institute in Washington, D.C., where he oversaw work in more than 30 states and provinces in North America, as well as the three regional multistate climate change programs.

He previously practiced environmental law with the Boston firm Brown Rudnick.